This study aims to investigate altered sleep patterns after surgical trauma. Gradations of trauma range from the relatively modest insult of herniorrhaphy, through cholecystectomy and gastrectomy, to conditions severe enough to require care in a surgical intensive care unit. Procedures of lesser severity were to provide baseline data with which to compare results in the intensive care unit. A series of herniorrhaphy, cholecystectomy, gastrectomy and total hip replacement patients have been studied. ICU studies are now in progress. ICU patients are studied daily for 16 to 24 hours. Major emphasis will be placed on: 1) the quality and quantity of sleep and those factors seemingly contributing to or detracting from sleep - the state of the patient's health, medication, nursing-doctors' procedures, machinery; 2) the relationship between sleep physiology and critical events in recovery or deterioration; 3) the prognostic significance of the presence or absence of persistent normal sleep patterning in severely ill patients who lapse into stupor or coma; and 4) the effects on patients discharged from the ICU of the sleep deprivation incurred there, especially such occurrences as cardio-respiratory irregularities in REM recovery. By precise tracking of clinical course and quality of sleep we will determine whether "better sleep" heralds, predicts or follows improvements in health.